Anchor for branch wellbore liner

ABSTRACT

An anchor for a branch wellbore liner. In a described embodiment, a system is used to anchor between an upper portion of a window formed through a sidewall of a first tubular string and an upper end of a second tubular string extending outwardly from the window. The system includes a first anchoring device at the upper portion of the window, and a second anchoring device at the upper end of the second tubular string. The first and second anchoring devices are operative to secure the upper end of the second tubular string to the upper portion of the window.

BACKGROUND

The present invention relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides an anchor for a branch wellbore liner.

In wells of the type known as multilateral wells, it is frequently the case that a liner string is conveyed into a branch or lateral wellbore through a window formed in a sidewall of a casing string in a parent or main wellbore. Sometimes, an upper end of the liner string is positioned in the branch wellbore spaced away from the casing string and is anchored in the branch wellbore using, for example, an inflatable packer. Other times it is desired to secure an upper end of the liner string to the casing string, for example, so that a mechanical, sand or pressure seal can be formed to isolate the interior of the casing and/or liner string from a formation surrounding the intersection of the parent and branch wellbores.

In the latter situation, typically either the liner string extends upwardly into the casing string above the window, or an upper portion of the liner string extending into the casing string is cut off after cementing the liner string in the branch wellbore. The first option obstructs access and flow through the casing string. The second option at times allows the remaining lower portion of the liner string to “spring back” into an interior of the casing string after the upper portion has been cut off. This is particularly troublesome at an upper end of the liner string, which is left relatively thin and flexible after the cutting procedure.

Therefore, it may be seen that it would be very desirable to provide improved systems and methods for anchoring a branch wellbore liner. Such systems and methods may find use in other applications, as well.

SUMMARY

In carrying out the principles of the present invention, in accordance with an embodiment thereof, a system and method are provided for anchoring a branch wellbore liner string to casing in a parent wellbore, without allowing the liner string to displace back into the casing, and without unduly obstructing access through the casing.

In one aspect of the invention, a system for anchoring between an upper portion of a window formed through a sidewall of a first tubular string and an upper end of a second tubular string extending outwardly from the window is provided. The system includes a first anchoring device at the upper portion of the window, and a second anchoring device at the upper end of the second tubular string. The first and second anchoring devices are operative to secure the upper end of the second tubular string to the upper portion of the window.

In another aspect of the invention, a system of anchoring a branch wellbore liner string to a casing string in a parent wellbore is provided. The system includes a first anchoring device of the casing string and a second anchoring device of the liner string. Engagement between the first and second anchoring devices prevents an upper end of the liner string from displacing inwardly relative to the casing string.

In yet another aspect of the invention, a method of anchoring a liner string to a casing string includes the steps of: conveying the liner string through a window formed through a sidewall of the casing string; and engaging a first anchoring device of the casing string with a second anchoring device of the liner string, thereby anchoring an upper terminal end of the liner string to the casing string.

These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an anchoring system and method embodying principles of the present invention;

FIG. 2 is a schematic cross-sectional view of the system and method of FIG. 1, in which further steps of the method have been performed;

FIG. 3 is an isometric view of an upper portion of a transition joint assembly in the system and method of FIG. 1;

FIG. 4 is a cross-sectional view of the transition joint assembly in a process of installation in a casing window joint;

FIG. 5 is a cross-sectional view of the transition joint assembly fully installed and anchored in the casing window joint;

FIG. 6 is a schematic cross-sectional view of a key of the transition joint assembly received in a keyway of the casing window joint, taken along line 6-6 of FIG. 5;

FIG. 7 is a schematic cross-sectional view of the key received in the keyway, taken along line 7-7 of FIG. 5;

FIG. 8 is an isometric view of a first alternate key configuration;

FIG. 9 is a schematic cross-sectional view of a first alternate keyway configuration;

FIG. 10 is a schematic cross-sectional view of a second alternate keyway configuration;

FIG. 11 is an isometric view of a second alternate key configuration;

FIG. 12 is an isometric view of a third alternate key configuration;

FIG. 13 is an isometric view of a fourth alternate key configuration;

FIG. 14 is a schematic cross-sectional view of the fourth alternate key configuration engaged with a third alternate keyway configuration;

FIG. 15 is a schematic cross-sectional view of a first seal configuration in the system and method of FIG. 1;

FIG. 16 is a schematic cross-sectional view of a second seal configuration in the system and method of FIG. 1;

FIG. 17 is a schematic cross-sectional view of a first alternate configuration of the system of FIG. 1;

FIG. 18 is a schematic cross-sectional view of a second alternate configuration of the system of FIG. 1;

FIG. 19 is a schematic cross-sectional view of another anchoring system and method embodying principles of the present invention;

FIG. 20 is a schematic cross-sectional view of yet another anchoring system and method embodying principles of the present invention; and

FIG. 21 is a cross-sectional view of an alternate configuration of a casing window joint embodying principles of the invention.

DETAILED DESCRIPTION

Representatively illustrated in FIG. 1 is an anchoring system 10 and associated method which embody principles of the present invention. It is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention.

As used herein, the terms “above” and “below,” “upper” and “lower,” and similar terms are used to indicate directions respectively closer to, and farther from, the surface along a wellbore, or along a tubular string in a wellbore. Thus, even in a perfectly horizontal wellbore, a portion of a tubular string in the wellbore which is closer to the surface along the wellbore than another portion of the tubular string is considered to be “above” the “lower” tubular string portion.

As depicted in FIG. 1, a casing string 12 has been installed in a parent or main wellbore 14. The casing string 12 is preferably, but not necessarily, cemented in the wellbore 14. A window joint 16 is interconnected in the casing string 12 at an intersection between the wellbore 14 and a branch or lateral wellbore 18.

The wellbore 18 extends outwardly from an opening or window 20 formed through a sidewall 22 of the window joint 16. The wellbore 18 could be drilled before or after the casing string 12 is installed in the wellbore 14, and the window 20 could be positioned at the intersection between the wellbores before or after it is formed through the sidewall 22. Thus, it should be clearly understood that the principles of the invention are not limited to any particular details or order of steps related herein for the various described embodiments. Instead, it should be recognized that a wide variety of changes, alternatives, options, etc. can be made in keeping with the principles of the invention.

Referring additionally now to FIG. 2, the system 10 is shown after a liner string 24 has been conveyed through the casing string 12, through the window 20, and into the branch wellbore 18. At this point, it should be understood that the use of the terms “casing string” and “liner string” is not to be taken as restricting the nature of the particular tubular strings designated by these terms. Instead, a “casing string” could include or be made up of casing, liner, tubing, or any other tubular structure. Likewise, a “liner string” could also include or be made up of casing, liner, tubing or any other tubular structure.

The liner string 24 includes a transition joint 26 which is specially configured so that it is complementarily shaped relative to the window joint 16. For example, the transition joint 26 has an inclined face 28 which is shaped so that it fits within the window 20, preferably without protruding into the interior of the casing string 12.

An anchor 30 is used to secure the liner string 24 to the casing string 12 at an upper portion of the window 20. Preferably, the anchor 30 prevents an upper terminal end 32 of the transition joint 26 from displacing inwardly or outwardly relative to the casing string 12. Note that, with the liner string 24 extending downwardly from the window 20, the liner string is suspended by the anchor 30 at the upper end 32, thereby producing tension in the liner string below the anchor.

Although the anchor 30 is schematically depicted in FIG. 2 as protruding into the interior of the casing string 12, preferably it does not in actual practice. The anchor 30 also preferably does not protrude into the interior of the liner string 24. Thus, the anchor 30 does not hinder access through either the casing string 12 or the liner string 24.

A seal 34 is used to seal between the casing string 12 and the liner string 24 at the interface between the transition joint 26 and the window 20. The seal 34 may be carried on the liner string 24 when it is conveyed through the casing string 12, or the seal could be positioned in the window 20 prior to installing the liner string. As another alternative, the seal 34 could be positioned between the casing and liner strings 12, 24 after the anchor 30 secures the transition joint 26 to the window joint 16.

The seal 34 is not necessarily a separate element of the system 10. For example, the seal 34 could be formed by expanding the transition joint 26 radially outward so that it makes contact with the window 20. This contact could form a metal-to-metal seal between the transition joint 26 and the window joint 16.

Whether or not the seal 34 is used in the system 10, the liner string 24 may be sealed and secured in the wellbore 18 by cement 36. Thus, either or both of the seal 34 and cement 36 may be used to prevent fluid, debris, sand, etc. from passing between the transition joint 26 and the window 20. In particular, the seal 34 and/or cement 36 can isolate interior fluid passages 38, 40 of the casing string 12 and liner string 24, respectively, from fluid communication with a formation 42 surrounding the intersection between the wellbores 14, 18.

Referring additionally now to FIG. 3, a particular embodiment of the transition joint 26 is representatively illustrated. Only an upper portion of the transition joint 26 is shown in FIG. 3, but in this view it may be seen that an anchoring device or key 44 is attached to the upper end 32 of the transition joint. The device 44 is one part of the anchor 30 schematically depicted in FIG. 2.

The device 44 is shown as being rigidly attached to the upper end 32 of the transition joint 26, for example, by welding the device to the transition joint. However, other methods of attaching the device 44 to the transition joint 26 could be used. The device 44 could be pivotably attached to the transition joint 26, or the device could be integrally formed on the transition joint, for example.

The device 44 includes a generally T-shaped upper end 46 having downwardly facing shoulders 56. The upper end 46 is shaped so that it operatively engages a cooperatively shaped recess, slot or keyway in the window joint 16, as described more fully below. However, it should be clearly understood that the device 44 (and the corresponding recess, slot or keyway) could have other shapes, and that the device could instead be attached to the window joint 16 while the recess, slot or keyway could be formed on the transition joint, without departing from the principles of the invention.

Referring additionally now to FIG. 4, the system 10 is depicted with the transition joint 26 being displaced downwardly through the window 20 of the window joint 16. The device 44 is rotationally aligned with another anchoring device 48 (not visible in FIG. 4, see FIG. 5), so that, as the transition joint 26 is displaced axially relative to the window joint 16, the device 44 will engage the device 48 to secure the upper end 32 of the transition joint to an upper portion 50 of the window 20.

Rotational alignment of the anchoring devices 44, 48 may be achieved using any appropriate method, some of which may be conventional. A running tool 52 (not shown in FIG. 4, see FIG. 17) could include an extendable dog or key which engages a slot or keyway in the casing string 12 above the window 20 in order to align the anchoring devices 44, 48. As another alternative, the transition joint 26 and window joint 16 could include elements which operate to align the anchoring devices 44, 48, one example of which is described below in relation to FIGS. 8 & 9.

Referring additionally now to FIG. 5, the system 10 is depicted after the device 44 has fully engaged the device 48, thereby securing the upper end 32 of the transition joint 26 at the upper portion 50 of the window 20. Note that the device 48 is formed in this embodiment as a recess or keyway in an increased thickness sidewall portion 54 of the window joint 16. The sidewall portion 54 has the increased thickness in order to provide ample space to accommodate the device 44 therein. However, it is not necessary for the device 44 to be received in an increased thickness sidewall portion in keeping with the principles of the invention. For example, the keyway device 48 could be attached to an interior surface of the window joint 16.

The manner in which the key device 44 engages the keyway device 48 may be more clearly seen in the schematic cross-sectional views depicted in FIGS. 6 & 7. In FIG. 6, the positioning of the key device 44 in the increased thickness sidewall portion 54 may be seen.

Note that the key device 44 is permitted to enter the keyway device 48 via a gap or opening 60 between the passage 38 and the keyway device. The running tool 52 may be used to bias the key device 44 laterally through the opening 60 into the keyway device 48. Alternatively, the key device 44 could be biased toward the keyway device 48 by its own resiliency. As another alternative, no biasing may be needed to laterally displace the key device 44 toward the keyway device 48, since lateral displacement of the transition joint 26 through the window 20 may also cause the key device to displace toward the keyway device. The branch wellbore 18 can be drilled in such a way that displacement of the transition joint 26 into the branch wellbore will bias the key device 44 toward the keyway device 48.

In FIG. 7, the key and keyway devices 44, 48 are shown from a side cross-sectional view. In this view, the manner in which the shoulders 56 on the device 44 contact and are supported by shoulders 58 formed in the device 48 may be seen. This contact and support prevents further downward and outward displacement of the transition joint 26 through the window 20, thereby also preventing inward or outward displacement of the upper end 32 relative to the window joint 16.

Disengagement of the key device 44 from the keyway device 48 may be prevented by optional locking devices 62. The locking devices 62 prevent upward displacement of the key device 44 relative to the keyway device 48, thereby preventing upward and inward displacement of the transition joint 26 relative to the window joint 16.

The locking devices 62 are depicted in FIG. 7 as each including a spring-biased dog, but any other types of locking devices may be used instead, such as ratchet mechanisms, gripping teeth, detents, etc. on either or both of the devices 44, 48. The locking devices 62 could be releasable (for example, by an appropriate releasing device carried on the running tool 52), if desired, to permit retrieval or repositioning of the liner string 24.

Referring additionally now to FIG. 8, the upper portion of the transition joint 26 is again illustrated, but with an alternate configuration of the key device 44. An additional outwardly extending shoulder 64 is now formed on the key lo device 44. This shoulder 64 may be used in rotationally aligning the key device 44 with the keyway device 48, as described in more detail below.

Referring additionally now to FIG. 9, an upper portion of the window joint 16 is depicted in a schematic cross-sectional view. As shown in FIG. 9, the window joint 16 has an alternate configuration in which a generally circumferentially extending recess or profile 66 is formed therein. A generally axially or longitudinally extending recess or slot 68 extends downwardly from the profile 66. Note that the slot 68 could be an upper portion of the keyway device 48.

As the key device 44 of FIG. 8 is conveyed downwardly through the passage, the shoulder 64 will eventually contact the profile 66. An indication of this engagement will be given at the surface, such as by a reduced hook load, at which time the transition joint 26 may be rotated so that the shoulder 64 is aligned with the slot 68. The profile 66 could be inclined downward toward the slot 68, so that engagement between the shoulder 64 and the profile will act to rotate the transition joint 26 so that the shoulder is aligned with the slot. Rotation of the transition joint 26 may be facilitated by use of a swivel joint in the liner string 24 below the transition joint.

When the shoulder 64 is aligned with the slot 68, the transition joint 26 will be permitted to displace downwardly, which may be indicated at the surface by an increased hook load. When the shoulder 64 is received in the slot 68, the key device 44 is aligned with the keyway device 48. Further downward displacement of the transition joint 26 relative to the window joint 16 will cause the key device 44 to operatively engage the keyway device 48.

Yet another option for rotationally aligning the key device 44 with the keyway device 48 could be to eliminate the profile 66. The transition joint 26 could then be positioned so that the key device 44 is within the upper portion of the window joint 16. The transition joint 26 would then be rotated until the shoulder 64 enters the slot 68, which would be indicated at the surface as an increased torque. At that point, the transition joint 26 would be lowered to operatively engage the key device 44 with the keyway device 48.

Referring additionally now to FIG. 9, another alternate configuration is illustrated. In this configuration, the keyway device 48 extends circumferentially in the sidewall portion 54 of the window joint 16. The transition joint 26 is rotated to displace the key device 44 into the keyway device 48 (from position 44 a to position 44 b as depicted in FIG. 9).

Thus, it may be seen that a variety of methods may be used to engage the key device 44 with the keyway device 48.

Referring additionally now to FIG. 11, an alternate configuration of the transition joint 26 is illustrated. In this configuration, the upper end 46 of the key device 44 has inclined downwardly facing shoulders 70 formed thereon. The inclined shoulders 70 may ease entry of the upper end 46 of the key device 44 into the keyway device 48 and, when engaged with complementarily shaped shoulders in the keyway device, operate to more accurately rotationally align the transition joint 26 with the window 20.

Referring additionally now to FIG. 12, another alternate configuration of the transition joint 26 is illustrated. In this configuration, the upper end 46 of the key device 44 has only a downwardly facing and outwardly extending shoulder 72 formed thereon. The shoulder 72 may be used both to rotationally align the devices 44, 48 (e.g., by engagement with the slot 68 as described above), and to support the transition joint 26 when the shoulder is engaged with an upwardly facing shoulder of the keyway device 48.

Referring additionally now to FIG. 13, yet another alternate configuration of the transition joint 26 is illustrated. In this configuration, the key device 44 has openings 74 formed therein, instead of shoulders. In FIG. 14, this key device 44 is shown engaged in the keyway device 48 from a schematic side cross-sectional view.

A locking device 76, which includes a spring-biased dog 78, is positioned proximate the keyway device 48. As the key device 44 is displaced downwardly in the keyway device 48, the opening 74 is eventually positioned opposite the dog 78, at which point the dog enters the opening and prevents further downward displacement of the key device 44. A separate locking device 76 may be provided for each of the openings 74 in the key device 44.

Referring additionally now to FIG. 15, an enlarged schematic cross-sectional view of the seal 34 is illustrated. As described above, the seal 34 could be carried on the transition joint 26, or it could be attached to the window joint 16 prior to conveying the liner string 24 through the window 20.

The seal 34 could be made of a material which swells (i.e., increases in volume) when exposed to fluid in the wellbores 14, 18. The seal 34 could be an expandable annular barrier, such as any of the annular barriers described in U.S. Published Application No. 2004/0055758, the entire disclosure of which is incorporated herein by this reference.

Also, as noted above, it is not necessary for the seal 34 to be a separate element. The transition joint 26 could, for example, be expanded within the window 20 to thereby form a seal between the transition joint and the window joint 16 by contact therebetween. If the transition joint 26 is expanded within the window 20, the separate seal 34 could still be used to seal between the expanded transition joint and the window joint 16.

Thus, the anchoring devices 44, 48 are operative to secure the upper end 32 of the liner string 24 to the upper portion 50 of the window 20 to allow the liner string to be expanded by using various internal expansion tools, which may include mechanical and/or hydraulic expansion tools. The liner string 24 could include other elements which are expanded also, such as sand control screens, annular isolation barriers, solid tubular sections, and combination thereof, etc.

Referring additionally now to FIG. 16, and alternate configuration of the seal 34 is illustrated. In this configuration, the seal 34 is a hardenable fluid which is flowed into a groove 78 formed on the window joint 16 about the window 20 via a passage 80 in the window joint. The seal 34 could, however, be flowed between the transition joint 26 and the window joint 16 without use of the groove 78. Furthermore, the groove 78 and/or passage 80 could be formed in the transition joint 26, instead of in the window joint 16.

The seal 34 could be any hardenable fluid, such as epoxies, other plastics, composites, gels, caulk-like substances, etc.

Referring additionally now to FIG. 17, an alternate configuration of the system 10 is schematically illustrated in which an additional anchoring device 82 is positioned on the liner string 24 spaced apart from and below the anchoring device 44 at the upper end 32 of the transition joint 26. The device 82 may be similar to the device 44.

Unfortunately, it sometimes happens that a liner string will become stuck while it is being run into a branch wellbore, or for some other reason it is not possible or desirable to fully install the liner string in the branch wellbore. If this should occur in the system 10 as depicted in FIG. 17, then the additional anchoring device 82 may still be used to anchor the liner string 24, even though the liner string is not fully installed in the branch wellbore 18.

The device 82 can be engaged with the device 48 in the window joint 16 to temporarily or permanently anchor the liner string 24. The liner string 24 may be temporarily anchored until a resolution is found for whatever problem prevented the liner string from being fully installed in the branch wellbore 18. If the problem cannot be resolved, then the liner string 24 may be permanently anchored using the device 82.

If the liner string 24 is permanently anchored using the device 82, then the portion of the liner string extending into the casing string 12 may be cut off to enhance access and flow through the passage 38 of the casing string. For example, a washover tool may be used to cut off the liner string 24 where it extends into the passage 38. The liner string 24 may be cemented in the branch wellbore 18 before or after this cutting operation, or not cemented at all.

Referring additionally now to FIG. 18, another alternate configuration of the system 10 is illustrated. In this configuration, multiple branch wellbores 18 are drilled which extend outwardly from respective window joints 16 interconnected in the casing string 12. Each branch wellbore 18 has a corresponding liner string 24 installed therein, with a transition joint 26 interconnected in the liner string and engaged with the respective window joint 16.

To permit selective installation of the liner strings 24 in the respective branch wellbores 18, different anchors 84, 86, 88 may be used. Each of the anchors 84, 86, 88 may include a set of the key device 44 and keyway device 48 as described above. However, the lowermost anchor 88 may have a dimension (such as width or thickness, etc.) which is greater than that of any of the anchors 84, 86 thereabove. Similarly, the next lowermost anchor 86 may have a dimension which is greater than that of the anchor 84 thereabove.

In this manner, the key device 44 of the anchor 88 will not operatively engage any of the keyway devices 48 of the upper anchors 84, 86 when a liner string 24 is installed in the lowermost branch wellbore 18. Likewise, the key device 44 of the anchor 86 will not operatively engage the keyway device 48 of the anchor 84 when a liner string 24 is installed in the middle branch wellbore 18. Thus, the system 10 permits selective completion of the branch wellbores 18 from the lowermost proceeding upward, in that each of the key devices 44 will not operatively engage any inappropriate keyway devices 48. However, other selection methods may be used, and the branch wellbores 18 may be completed in different orders, without departing from the principles of the invention.

Referring additionally now to FIG. 19, another system 90 and associated method embodying principles of the present invention is illustrated. In the system 90, a liner string 92 is conveyed into a branch wellbore 100 through a window 94 formed through a sidewall of a casing string 96. When installed, the liner string 92 extends into a flow passage 102 of the casing string 96.

With the liner string 92 extending into the passage 102, the liner string is cemented in the branch wellbore 10. After the cement has set, the portion of the liner string 92 extending into the passage 102 is cut off, for example, by using a washover tool, and retrieved from the passage.

To prevent an upper terminal end 104 of the liner string 92 from displacing inwardly relative to the casing string 96, an anchor 106 is used in the system 90. The anchor 106 is similar to the anchors 30, 84, 86, 88 described above. For example, the anchor 106 may include the keyway anchoring device 48 formed in the casing string 96 at an upper portion of the window 94.

However, the anchor 106 differs in one significant respect from the anchors 30, 84, 86, 88 in that it includes a key anchoring device 108 which is separately conveyed into the casing string 96 after the liner string 92 is cut off. That is, the key anchoring device 108 is positioned in the casing string 96 and engaged with the keyway device 48 to prevent inward displacement of the upper end 104 of the liner string 92. The key device 108 may be configured similar in many respects to the key device 44 described above (particularly in those respects which facilitate engagement with the keyway device 48), but unlike the key device 44, the key device 108 is not attached to a transition joint of the liner string 92 when it is conveyed through the casing string 96.

Referring additionally now to FIG. 20, another system 110 and associated method are representatively illustrated. The system 110 is similar in most respects to the system 10 described above, and so elements shown in FIG. 20 which are similar to those described above are indicated using the same reference numbers.

The system 110 differs in one substantial respect from the system 10 in that the liner string 24 is secured at a lower end of the window 20 using a second anchor 112. Thus, in the system 110, the liner string 24 is secured both at the upper end and at the lower end of the window 20.

The anchor 112 may be similar to the anchor 30 as described above, including any of the alternate configurations described above, or the anchor 112 could be of a different type. For example, the anchor used at a lower end of a window in the LTBS™ system available from Halliburton Energy Services, Inc. of Houston, Tex. and described in U.S. Pat. No. 5,458,209, the entire disclosure of which is incorporated herein by this reference, could be used for the anchor 112. Alternatively, the anchor used at a lower end of a window in the HOOK Hanger™ system available from Baker Oil Tools of Houston, Tex. could be used for the anchor 112. Thus, a variety of anchors, anchoring devices and means of securing tubular strings may be used in keeping with the principles of the invention.

Referring additionally now to FIG. 21, a cross-sectional view of an alternate configuration of a casing window joint 120 is representatively illustrated. The window joint 120 may be used in any of the systems 10, 90, 110 and methods described above. For example, the window joint 120 could be used for the window joint 16 in the system 10.

The window joint 120 differs in one substantial respect from the window joint 16 in that it has a consistent thickness sidewall 122, i.e., it has an interior flow passage 124 which is generally concentric with an outer diameter 126 of the window joint 120. Another difference is that the window joint 120 has an anchoring device 128 which is formed at least partially on a member 130 attached externally to the sidewall 122. The member 130 could alternatively be attached to an interior of the sidewall 122, if desired. The member 130 could be attached using fasteners, by welding, or by any other method.

Use of the member 130 increases the thickness of the sidewall 122 in the area where the anchoring device 128 is located, without significantly increasing the cost of fabricating the window joint 120. The thickness of the sidewall 122 may be increased by any other method in keeping with the principles of the invention.

The anchoring device 128 is depicted in FIG. 21 as including a keyway, similar to the keyway 48 described above for engagement with the key 44, but other types of anchoring devices may be used in keeping with the principles of the invention. If the window joint 120 is used in the method 110, then two of the anchoring devices 128 may be used, one above and one below a window formed through the sidewall 122 (similar to the window 20 in the window joint 16).

Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are contemplated by the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents. 

1. A system for anchoring between an upper portion of a window formed through a sidewall of a first tubular string and an upper end of a second tubular string extending outwardly from the window, the system comprising: a first anchoring device at the upper portion of the window; and a second anchoring device at the upper end of the second tubular string, the first and second anchoring devices being operative to secure the upper end of the second tubular string to the upper portion of the window.
 2. The system of claim 1, wherein engagement between the first and second anchoring devices prevents the upper end of the second tubular string from displacing inwardly relative to the first tubular string.
 3. The system of claim 1, wherein engagement between the first and second anchoring devices prevents the upper end of the second tubular string from displacing outwardly relative to the first tubular string.
 4. The system of claim 1, wherein the second anchoring device is rigidly attached to the upper end of the second tubular string.
 5. The system of claim 1, wherein the second anchoring device is installed in the first tubular string after the second tubular string is conveyed through the window.
 6. The system of claim 1, wherein engagement between the first and second anchoring devices produces tension in an upper portion of the second tubular string.
 7. The system of claim 1, wherein engagement between the first and second anchoring devices suspends the second tubular string from the upper end of the second tubular string.
 8. The system of claim 1, further comprising a seal between the second tubular string and the window.
 9. The system of claim 1, further comprising a third anchoring device on the second tubular string, the first and third anchoring devices being operative to secure the second tubular string to the upper portion of the window.
 10. The system of claim 1, wherein the first anchoring device is formed in a portion of the sidewall of the first tubular string having an increased wall thickness.
 11. The system of claim 1, wherein the first anchoring device is formed at least partially on a member attached to the first tubular string.
 12. The system of claim 1, wherein engagement between the first and second anchoring devices rotationally aligns the first and second tubular strings.
 13. The system of claim 1, wherein the second tubular string is secured at a lower end of the window.
 14. The system of claim 13, wherein the second tubular string is secured at an upper end of the window.
 15. A system for anchoring a branch wellbore liner string to a casing string in a parent wellbore, the system comprising: a first anchoring device of the casing string; and a second anchoring device of the liner string, engagement between the first and second anchoring devices preventing an upper end of the liner string from displacing inwardly relative to the casing string.
 16. The system of claim 15, wherein the first anchoring device comprises a keyway formed in a sidewall of the casing string.
 17. The system of claim 16, wherein the keyway is formed in an increased wall thickness portion of the casing string sidewall.
 18. The system of claim 16, wherein the second anchoring device comprises a key at an upper end of the liner string.
 19. The system of claim 18, wherein the key is attached at an upper end of a transition joint of the liner string.
 20. The system of claim 19, wherein the transition joint is complementarily shaped relative to a window formed through the sidewall of the casing string.
 21. The system of claim 18, wherein the key engages a shoulder of the keyway to thereby prevent outward displacement of the liner string relative to the casing string.
 22. The system of claim 18, wherein a locking device prevents disengagement of the key from the keyway.
 23. The system of claim 15, wherein the second anchoring device is free of any protrusion into a longitudinal flow passage of the casing string when the first and second anchoring devices are operatively engaged.
 24. The system of claim 15, wherein the first and second anchoring devices are operatively engaged by relative axial displacement between the first and second anchoring devices.
 25. The system of claim 15, wherein the first and second anchoring devices are operatively engaged by relative rotational displacement between the first and second anchoring devices.
 26. The system of claim 15, wherein the first and second anchoring devices rotationally align the liner string relative to the casing string.
 27. The system of claim 15, further comprising a locking device which prevents disengagement of the first and second anchoring devices after the first and second anchoring devices are engaged.
 28. The system of claim 15, wherein the second anchoring device is rigidly attached to the upper end of the liner string.
 29. The system of claim 15, wherein the second anchoring device is installed in the casing string after the liner string is conveyed through a window formed through a sidewall of the casing string.
 30. The system of claim 15, wherein engagement between the first and second anchoring devices produces tension in an upper portion of the liner string.
 31. The system of claim 15, wherein engagement between the first and second anchoring devices suspends the liner string from the upper end of the liner string.
 32. The system of claim 15, further comprising a seal between the liner string and the casing string about a window formed through a sidewall of the casing string.
 33. The system of claim 32, wherein the seal is carried on the liner string as the liner string is conveyed through the casing string.
 34. The system of claim 32, wherein the seal is carried on the casing string.
 35. The system of claim 32, wherein the seal is positioned between the liner and casing strings after the liner string is conveyed through the casing string.
 36. The system of claim 32, wherein the seal is a hardenable fluid flowed between the liner and casing strings after the liner string is conveyed through the casing string.
 37. The system of claim 32, wherein the seal is made of a material which swells between the liner and casing strings.
 38. The system of claim 37, wherein the material swells when contacted by fluid in a wellbore.
 39. The system of claim 32, wherein the seal is formed by expanding the liner string after the liner string is conveyed through the casing string.
 40. The system of claim 15, further comprising a third anchoring device on the liner string below the second anchoring device, the first and third anchoring devices being operative to secure the liner string to the casing string.
 41. The system of claim 15, wherein the first anchoring device is formed in a portion of a sidewall of the casing string having an increased wall thickness.
 42. The system of claim 41, wherein the first anchoring device is a keyway formed in the increased wall thickness sidewall portion, and wherein the second anchoring device is a key cooperatively engageable with the keyway.
 43. The system of claim 15, wherein the casing string includes multiple first anchoring devices, and wherein each of multiple liner strings has a respective second anchoring device engaged with a corresponding one of the first anchoring devices.
 44. The system of claim 43, wherein each of the second anchoring devices is configured for selective engagement with only the corresponding one of the first anchoring devices.
 45. The system of claim 15, wherein the first anchoring device is formed in an increased wall thickness portion of a sidewall of the casing string.
 46. The system of claim 15, wherein the first anchoring device is formed at least partially on a member attached to the casing string.
 47. The system of claim 15, wherein the liner string is secured at a lower end of a window formed through a sidewall of the casing string.
 48. The system of claim 47, wherein the liner string is secured at an upper end of the window.
 49. The system of claim 15, wherein the second anchoring device is free of any protrusion into a longitudinal flow passage of the liner string when the first and second anchoring devices are operatively engaged.
 50. The system of claim 15, further comprising a running tool for installing the liner string, the running tool being operative to bias the second anchoring device into engagement with the first anchoring device.
 51. A method of anchoring a liner string to a casing string, the method comprising the steps of: conveying the liner string through a window formed through a sidewall of the casing string; and engaging a first anchoring device of the casing string with a second anchoring device of the liner string, thereby anchoring an upper terminal end of the liner string to the casing string.
 52. The method of claim 51, wherein the engaging step further comprises displacing the second anchoring device with the liner string as the liner string is conveyed through the window.
 53. The method of claim 51, wherein the first anchoring device is a keyway recessed into a sidewall of the casing string, wherein the second anchoring device is a key, and wherein the engaging step further comprises displacing the key at least partially through the keyway.
 54. The method of claim 53, further comprising the steps of providing the casing string sidewall having an increased wall thickness portion, and forming the keyway in the increased wall thickness portion.
 55. The method of claim 51, wherein the engaging step further comprises displacing the second anchoring device axially relative to the first anchoring device.
 56. The method of claim 51, wherein the engaging step further comprises displacing the second anchoring device rotationally relative to the first anchoring device.
 57. The method of claim 51, further comprising the step of preventing disengagement of the first and second anchoring devices after the engaging step.
 58. The method of claim 51, further comprising the step of rotationally aligning the first and second anchoring devices prior to the engaging step.
 59. The method of claim 58, wherein the rotationally aligning step further comprises engaging a shoulder on the second anchoring device with a circumferentially extending profile formed in the casing string.
 60. The method of claim 51, further comprising the step of sealing between the liner string and the casing string.
 61. The method of claim 60, wherein the sealing step further comprises positioning a seal between the liner and casing strings.
 62. The method of claim 60, wherein the sealing step further comprises flowing a hardenable fluid between the liner and casing strings.
 63. The method of claim 60, wherein the sealing step further comprises swelling a material between the liner and casing strings.
 64. The method of claim 60, wherein the sealing step further comprises expanding the liner string within the window.
 65. The method of claim 51, wherein the anchoring step further comprises preventing the upper terminal end of the liner string from displacing inwardly relative to the casing string.
 66. The method of claim 51, wherein the anchoring step further comprises preventing the upper terminal end of the liner string from displacing outwardly relative to the casing string.
 67. The method of claim 51, further comprising the step of positioning the second anchoring device in the casing string after the conveying step.
 68. The method of claim 67, wherein the positioning step is performed after cutting off an upper portion of the liner string in the casing string.
 69. The method of claim 51, wherein the engaging step further comprises securing the upper terminal end of the liner string to an upper portion of the window, and further comprising the step of after the engaging step expanding the liner string within the window using a selected one or more of mechanical and hydraulic expansion tools.
 70. The method of claim 69, wherein the expanding step further comprises expanding a selected one or more of a sand control screen, an annular isolation barrier and a solid tubular section included in the liner string.
 71. The method of claim 51, further comprising the steps of forming the first anchoring device at least partially on a member, and attaching the member to the casing string.
 72. The method of claim 51, further comprising the step of cutting off a portion of the liner string extending into the casing string, after the engaging step.
 73. The method of claim 51, further comprising the step of securing the liner string at a lower end of the window.
 74. The method of claim 73, wherein the engaging step further comprises securing the liner string at an upper end of the window.
 75. The method of claim 51, wherein after the engaging step, the casing string is free of any protrusion of the first and second anchoring devices into a longitudinal flow passage of the casing string.
 76. The method of claim 51, wherein after the engaging step, the liner string is free of any protrusion of the first and second anchoring devices into a longitudinal flow passage of the liner string.
 77. The method of claim 51, further comprising the step of biasing the second anchoring device into engagement with the first anchoring device.
 78. The method of claim 77, wherein the biasing step is performed by a running tool used in the conveying step to install the liner string. 